Nice picture
(though I’m not good at estimating actual size range, eg, 2-10mm or 4-20mm?)
Various sizes of gravel so it shouldn’t pack tightly (less chances of anaerobic areas forming) but it also allows small particles to sink into the gravel bed - you can check for this by pushing your siphon tube deeply into the gravel as one end of the tank (during a water change)
(I use a Python water changing system so that’s the size/type of siphon tube I’m assuming for this substrate check)
I looked and found your algae/plant topic, this + the 12year old substrate makes it more likely that there will be loads of built up debris
I don’t recall what filter you have on the tank, this may need to be well rinsed to remove any built up debris
Obviously it’s more economic to clean your current substrate, but it’s also fairly water/labour intensive
Filipe Oliveira VLOG Step by Step Rescape
Although his substrate is Aquarium Soil rather than gravel, I suspect you’ll see similar (or possibly even more) levels of debris
EcoComplete is a “natural” substrate which acts very differently than the coated “black” gravels - if your old substrate is coated, I’d likely just bin it
Then consider budget and plant goals, fish needs, maintenance goals etc
Carib Sea also has a Soil based product “Samurai Soil” which you might investigate - CS claims “
without the muddy texture and crumbling often seen with other brands.” - but I’ve not seen the product or know much about its use (maybe check US forums)
If you compare a product to ADA Africana, it’s easy to maintain Samurai Soil claims ... but if compared to Tropica Aquarium Soil (which I consider one of the best integrity Aquarium Soils), is Samurai Soil better/worse performing .....
As you have larger fish, do they dig/sift through substrate?
- look at species behaviour as well as what you’ve observed personally - if your present substrate is less compatible with sifting behaviour, you may see little substrate disturbance with present fish, then when you replace the substrate, this may change
Given your fish list, I’d stick with fairly sturdy plants, if you don’t want to add CO2, choose plants with low CO2 requirement (Tropica website usually includes CO2 as low, medium, high) - of course these will also be slower growing plants, so only low levels of fertilizers are needed
I’d probably rescape your tank with defined plant areas (using Aquarium soil or combination of Aquarium Soil and fine gravel (upper layer)), some epiphyte plants (Anubias, Buces, Microsorum etc) on large pieces of wood, then a thin sand layer elsewhere (easy to clean or replace occasionally (if you choose an off-white color), good for substrate sifting)
Some very nice tank scapes in this journal
Scape corner
@Jayefc1
https://www.ukaps.org/forum/threads/scape-corner.57131/